<?php

/**
 * This class provides a simple interface for OpenID (1.1 and 2.0) authentication.
 * Supports Yadis discovery.
 * The authentication process is stateless/dumb.
 *
 * Usage:
 * Sign-on with OpenID is a two step process:
 * Step one is authentication with the provider:
 * <code>
 * $openid = new LightOpenID;
 * $openid->identity = 'ID supplied by user';
 * header('Location: ' . $openid->authUrl());
 * </code>
 * The provider then sends various parameters via GET, one of them is openid_mode.
 * Step two is verification:
 * <code>
 * if ($this->data['openid_mode']) {
 *     $openid = new LightOpenID;
 *     echo $openid->validate() ? 'Logged in.' : 'Failed';
 * }
 * </code>
 *
 * Optionally, you can set $returnUrl and $realm (or $trustRoot, which is an alias).
 * The default values for those are:
 * $openid->realm     = (!empty($_SERVER['HTTPS']) ? 'https' : 'http') . '://' . $_SERVER['HTTP_HOST'];
 * $openid->returnUrl = $openid->realm . $_SERVER['REQUEST_URI'];
 * If you don't know their meaning, refer to any openid tutorial, or specification. Or just guess.
 *
 * AX and SREG extensions are supported.
 * To use them, specify $openid->required and/or $openid->optional before calling $openid->authUrl().
 * These are arrays, with values being AX schema paths (the 'path' part of the URL).
 * For example:
 *   $openid->required = array('namePerson/friendly', 'contact/email');
 *   $openid->optional = array('namePerson/first');
 * If the server supports only SREG or OpenID 1.1, these are automaticaly
 * mapped to SREG names, so that user doesn't have to know anything about the server.
 *
 * To get the values, use $openid->getAttributes().
 *
 *
 * The library requires PHP >= 5.1.2 with curl or http/https stream wrappers enabled.
 * @author Mewp
 * @copyright Copyright (c) 2010, Mewp
 * @license http://www.opensource.org/licenses/mit-license.php MIT
 */
class LightOpenID
{
    public $returnUrl, $required = array(), $optional = array(), $verify_peer = null, $capath = null, $cainfo = null;
    private $identity, $claimed_id;
    protected $server, $version, $trustRoot, $aliases, $identifier_select = false, $ax = false, $sreg = false, $data;
    static protected $ax_to_sreg = array( //
        'namePerson/friendly' => 'nickname', //
        'contact/email' => 'email', //
        'namePerson' => 'fullname', //
        'birthDate' => 'dob', //
        'person/gender' => 'gender', //
        'contact/postalCode/home' => 'postcode', //
        'contact/country/home' => 'country', //
        'pref/language' => 'language', //
        'pref/timezone' => 'timezone', //
        'namePerson/first' => 'firstname', //google - NV
        'namePerson/last' => 'lastname' //google - NV
        );

    function __construct()
    {
        if ( ! function_exists( 'curl_init' ) && ! in_array( 'https', stream_get_wrappers() ) )
        {
            trigger_error( 'You must have either https wrappers or curl enabled.', 256 );
        }

        $this->trustRoot = ( ( isset( $_SERVER['HTTPS'] ) and strtolower( $_SERVER['HTTPS'] ) == 'on' ) ? 'https' : 'http' ) . '://' . $_SERVER['HTTP_HOST'];
        $uri = rtrim( preg_replace( '#((?<=\?)|&)openid\.[^&]+#', '', $_SERVER['REQUEST_URI'] ), '?' );
        $this->returnUrl = $this->trustRoot . $uri;

        $this->data = $_POST + $_GET; # OPs may send data as POST or GET.
    }

    function __set( $name, $value )
    {
        switch ( $name )
        {
            case 'identity':
                if ( strlen( $value = trim( ( string )$value ) ) )
                {
                    if ( preg_match( '#^xri:/*#i', $value, $m ) )
                    {
                        $value = substr( $value, strlen( $m[0] ) );
                    } elseif ( ! preg_match( '/^(?:[=@+\$!\(]|https?:)/i', $value ) )
                    {
                        $value = "http://" . $value;
                    }
                    if ( preg_match( '#^https?://[^/]+$#i', $value, $m ) )
                    {
                        $value .= '/';
                    }
                }
                $this->$name = $this->claimed_id = $value;
                break;
            case 'trustRoot':
            case 'realm':
                $this->trustRoot = trim( $value );
        }
    }

    function __get( $name )
    {
        if ( $name == 'identity' ) return $this->claimed_id;
        if ( $name == 'trustRoot' or $name == 'realm' ) return $this->trustRoot;
        if ( $name == 'mode' ) return empty( $this->data['openid_mode'] ) ? null : $this->data['openid_mode'];
    }

    /**
     * Checks if the server specified in the url exists.
     *
     * @param $url url to check
     * @return true, if the server exists; false otherwise
     */
    function hostExists( $url )
    {
        if ( strpos( $url, '/' ) === false )
        {
            $server = $url;
        }
        else
        {
            $server = @parse_url( $url, PHP_URL_HOST );
        }

        if ( ! $server )
        {
            return false;
        }

        return ! ! gethostbynamel( $server );
    }

    protected function request_curl( $url, $method = 'GET', $params = array() )
    {
        $params = http_build_query( $params, '', '&' );
        $curl = curl_init( $url . ( $method == 'GET' && $params ? '?' . $params : '' ) );
        $safe_mode = ( ini_get( 'safe_mode' ) == '1' || strtolower( ini_get( 'safe_mode' ) ) == 'on' ) ? 1 : 0;
        $open_basedir = ( ini_get( 'open_basedir' ) == '1' || strtolower( ini_get( 'open_basedir' ) ) == 'on' ) ? 1 : 0;
        if ( ! $safe_mode and $open_basedir )
        {
            curl_setopt( $curl, CURLOPT_FOLLOWLOCATION, true );
        }
        curl_setopt( $curl, CURLOPT_HEADER, false );
        curl_setopt( $curl, CURLOPT_SSL_VERIFYPEER, false );
        curl_setopt( $curl, CURLOPT_RETURNTRANSFER, true );
        curl_setopt( $curl, CURLOPT_HTTPHEADER, array( 'Accept: application/xrds+xml, */*' ) );

        if ( $this->verify_peer !== null )
        {
            curl_setopt( $curl, CURLOPT_SSL_VERIFYPEER, $this->verify_peer );
            if ( $this->capath )
            {
                curl_setopt( $curl, CURLOPT_CAPATH, $this->capath );
            }

            if ( $this->cainfo )
            {
                curl_setopt( $curl, CURLOPT_CAINFO, $this->cainfo );
            }
        }

        if ( $method == 'POST' )
        {
            curl_setopt( $curl, CURLOPT_POST, true );
            curl_setopt( $curl, CURLOPT_POSTFIELDS, $params );
        } elseif ( $method == 'HEAD' )
        {
            curl_setopt( $curl, CURLOPT_HEADER, true );
            curl_setopt( $curl, CURLOPT_NOBODY, true );
        }
        else
        {
            curl_setopt( $curl, CURLOPT_HTTPGET, true );
        }
        $response = curl_exec( $curl );

        if ( $method == 'HEAD' )
        {
            $headers = array();
            foreach ( explode( "\n", $response ) as $header )
            {
                $pos = strpos( $header, ':' );
                $name = strtolower( trim( substr( $header, 0, $pos ) ) );
                $headers[$name] = trim( substr( $header, $pos + 1 ) );
            }

            # Updating claimed_id in case of redirections.
            $effective_url = curl_getinfo( $curl, CURLINFO_EFFECTIVE_URL );
            if ( $effective_url != $url )
            {
                $this->identity = $this->claimed_id = $effective_url;
            }

            return $headers;
        }

        if ( curl_errno( $curl ) )
        {
            trigger_error( 'Curl error: ' . curl_error( $curl ), 256 );
        }

        return $response;
    }

    protected function request_streams( $url, $method = 'GET', $params = array() )
    {
        if ( ! $this->hostExists( $url ) )
        {
            trigger_error( 'Invalid request.', 256 );
        }

        $params = http_build_query( $params, '', '&' );
        switch ( $method )
        {
            case 'GET':
                $opts = array( 'http' => array( 'method' => 'GET', 'header' => 'Accept: application/xrds+xml, */*', 'ignore_errors' => true, ) );
                $url = $url . ( $params ? '?' . $params : '' );
                break;
            case 'POST':
                $opts = array( 'http' => array( 'method' => 'POST', 'header' => 'Content-type: application/x-www-form-urlencoded', 'content' => $params, 'ignore_errors' => true, ) );
                break;
            case 'HEAD':
                # We want to send a HEAD request,
                # but since get_headers doesn't accept $context parameter,
                # we have to change the defaults.
                $default = stream_context_get_options( stream_context_get_default() );
                stream_context_get_default( array( 'http' => array( 'method' => 'HEAD', 'header' => 'Accept: application/xrds+xml, */*', 'ignore_errors' => true, ) ) );

                $url = $url . ( $params ? '?' . $params : '' );
                $headers_tmp = get_headers( $url );
                if ( ! $headers_tmp )
                {
                    return array();
                }

                # Parsing headers.
                $headers = array();
                foreach ( $headers_tmp as $header )
                {
                    $pos = strpos( $header, ':' );
                    $name = strtolower( trim( substr( $header, 0, $pos ) ) );
                    $headers[$name] = trim( substr( $header, $pos + 1 ) );

                    # Following possible redirections. The point is just to have
                    # claimed_id change with them, because get_headers() will
                    # follow redirections automatically.
                    # We ignore redirections with relative paths.
                    # If any known provider uses them, file a bug report.
                    if ( $name == 'location' )
                    {
                        if ( strpos( $headers[$name], 'http' ) === 0 )
                        {
                            $this->identity = $this->claimed_id = $headers[$name];
                        } elseif ( $headers[$name][0] == '/' )
                        {
                            $parsed_url = parse_url( $this->claimed_id );
                            $this->identity = $this->claimed_id = $parsed_url['scheme'] . '://' . $parsed_url['host'] . $headers[$name];
                        }
                    }
                }

                # And restore them.
                stream_context_get_default( $default );
                return $headers;
        }

        if ( $this->verify_peer )
        {
            $opts += array( 'ssl' => array( 'verify_peer' => true, 'capath' => $this->capath, 'cafile' => $this->cainfo, ) );
        }

        $context = stream_context_create( $opts );

        return file_get_contents( $url, false, $context );
    }

    protected function request( $url, $method = 'GET', $params = array() )
    {
        if ( function_exists( 'curl_init' ) && ! ini_get( 'safe_mode' ) && ! ini_get( 'open_basedir' ) )
        {
            return $this->request_curl( $url, $method, $params );
        }
        return $this->request_streams( $url, $method, $params );
    }

    protected function build_url( $url, $parts )
    {
        if ( isset( $url['query'], $parts['query'] ) )
        {
            $parts['query'] = $url['query'] . '&' . $parts['query'];
        }

        $url = $parts + $url;
        $url = $url['scheme'] . '://' . ( empty( $url['username'] ) ? '' : ( empty( $url['password'] ) ? "{$url['username']}@" : "{$url['username']}:{$url['password']}@" ) ) . $url['host'] . ( empty( $url['port'] ) ? '' : ":{$url['port']}" ) . ( empty( $url['path'] ) ? '' : $url['path'] ) . ( empty( $url['query'] ) ? '' : "?{$url['query']}" ) . ( empty( $url['fragment'] ) ? '' : "#{$url['fragment']}" );
        return $url;
    }

    /**
     * Helper function used to scan for <meta>/<link> tags and extract information
     * from them
     */
    protected function htmlTag( $content, $tag, $attrName, $attrValue, $valueName )
    {
        preg_match_all( "#<{$tag}[^>]*$attrName=['\"].*?$attrValue.*?['\"][^>]*$valueName=['\"](.+?)['\"][^>]*/?>#i", $content, $matches1 );
        preg_match_all( "#<{$tag}[^>]*$valueName=['\"](.+?)['\"][^>]*$attrName=['\"].*?$attrValue.*?['\"][^>]*/?>#i", $content, $matches2 );

        $result = array_merge( $matches1[1], $matches2[1] );
        return empty( $result ) ? false : $result[0];
    }

    /**
     * Performs Yadis and HTML discovery. Normally not used.
     * @param $url Identity URL.
     * @return String OP Endpoint (i.e. OpenID provider address).
     * @throws ErrorException
     */
    function discover( $url )
    {
        if ( ! $url ) trigger_error( 'No identity supplied.', 256 );
        # Use xri.net proxy to resolve i-name identities
        if ( ! preg_match( '#^https?:#', $url ) )
        {
            $url = "https://xri.net/" . $url;
        }

        # We save the original url in case of Yadis discovery failure.
        # It can happen when we'll be lead to an XRDS document
        # which does not have any OpenID2 services.
        $originalUrl = $url;

        # A flag to disable yadis discovery in case of failure in headers.
        $yadis = true;

        # We'll jump a maximum of 5 times, to avoid endless redirections.
        for ( $i = 0; $i < 5; $i++ )
        {
            if ( $yadis )
            {
                $headers = $this->request( $url, 'HEAD' );

                $next = false;
                if ( isset( $headers['x-xrds-location'] ) )
                {
                    $url = $this->build_url( parse_url( $url ), parse_url( trim( $headers['x-xrds-location'] ) ) );
                    $next = true;
                }

                if ( isset( $headers['content-type'] ) && ( strpos( $headers['content-type'], 'application/xrds+xml' ) !== false || strpos( $headers['content-type'], 'text/xml' ) !== false ) )
                {
                    # Apparently, some providers return XRDS documents as text/html.
                    # While it is against the spec, allowing this here shouldn't break
                    # compatibility with anything.
                    # ---
                    # Found an XRDS document, now let's find the server, and optionally delegate.
                    $content = $this->request( $url, 'GET' );

                    preg_match_all( '#<Service.*?>(.*?)</Service>#s', $content, $m );
                    foreach ( $m[1] as $content )
                    {
                        $content = ' ' . $content; # The space is added, so that strpos doesn't return 0.

                        # OpenID 2
                        $ns = preg_quote( 'http://specs.openid.net/auth/2.0/' );
                        if ( preg_match( '#<Type>\s*' . $ns . '(server|signon)\s*</Type>#s', $content, $type ) )
                        {
                            if ( $type[1] == 'server' ) $this->identifier_select = true;

                            preg_match( '#<URI.*?>(.*)</URI>#', $content, $server );
                            preg_match( '#<(Local|Canonical)ID>(.*)</\1ID>#', $content, $delegate );
                            if ( empty( $server ) )
                            {
                                return false;
                            }
                            # Does the server advertise support for either AX or SREG?
                            $this->ax = ( bool )strpos( $content, '<Type>http://openid.net/srv/ax/1.0</Type>' );
                            $this->sreg = strpos( $content, '<Type>http://openid.net/sreg/1.0</Type>' ) || strpos( $content, '<Type>http://openid.net/extensions/sreg/1.1</Type>' );

                            $server = $server[1];
                            if ( isset( $delegate[2] ) ) $this->identity = trim( $delegate[2] );
                            $this->version = 2;

                            $this->server = $server;
                            return $server;
                        }

                        # OpenID 1.1
                        $ns = preg_quote( 'http://openid.net/signon/1.1' );
                        if ( preg_match( '#<Type>\s*' . $ns . '\s*</Type>#s', $content ) )
                        {

                            preg_match( '#<URI.*?>(.*)</URI>#', $content, $server );
                            preg_match( '#<.*?Delegate>(.*)</.*?Delegate>#', $content, $delegate );
                            if ( empty( $server ) )
                            {
                                return false;
                            }
                            # AX can be used only with OpenID 2.0, so checking only SREG
                            $this->sreg = strpos( $content, '<Type>http://openid.net/sreg/1.0</Type>' ) || strpos( $content, '<Type>http://openid.net/extensions/sreg/1.1</Type>' );

                            $server = $server[1];
                            if ( isset( $delegate[1] ) ) $this->identity = $delegate[1];
                            $this->version = 1;

                            $this->server = $server;
                            return $server;
                        }
                    }

                    $next = true;
                    $yadis = false;
                    $url = $originalUrl;
                    $content = null;
                    break;
                }
                if ( $next ) continue;

                # There are no relevant information in headers, so we search the body.
                $content = $this->request( $url, 'GET' );
                $location = $this->htmlTag( $content, 'meta', 'http-equiv', 'X-XRDS-Location', 'content' );
                if ( $location )
                {
                    $url = $this->build_url( parse_url( $url ), parse_url( $location ) );
                    continue;
                }
            }

            if ( ! $content ) $content = $this->request( $url, 'GET' );

            # At this point, the YADIS Discovery has failed, so we'll switch
            # to openid2 HTML discovery, then fallback to openid 1.1 discovery.
            $server = $this->htmlTag( $content, 'link', 'rel', 'openid2.provider', 'href' );
            $delegate = $this->htmlTag( $content, 'link', 'rel', 'openid2.local_id', 'href' );
            $this->version = 2;

            if ( ! $server )
            {
                # The same with openid 1.1
                $server = $this->htmlTag( $content, 'link', 'rel', 'openid.server', 'href' );
                $delegate = $this->htmlTag( $content, 'link', 'rel', 'openid.delegate', 'href' );
                $this->version = 1;
            }

            if ( $server )
            {
                # We found an OpenID2 OP Endpoint
                if ( $delegate )
                {
                    # We have also found an OP-Local ID.
                    $this->identity = $delegate;
                }
                $this->server = $server;
                return $server;
            }

            trigger_error( 'No servers found!', 256 );
        }
        trigger_error( 'Endless redirection!', 256 );
    }

    protected function sregParams()
    {
        $params = array();
        # We always use SREG 1.1, even if the server is advertising only support for 1.0.
        # That's because it's fully backwards compatibile with 1.0, and some providers
        # advertise 1.0 even if they accept only 1.1. One such provider is myopenid.com
        $params['openid.ns.sreg'] = 'http://openid.net/extensions/sreg/1.1';
        if ( $this->required )
        {
            $params['openid.sreg.required'] = array();
            foreach ( $this->required as $required )
            {
                if ( ! isset( self::$ax_to_sreg[$required] ) ) continue;
                $params['openid.sreg.required'][] = self::$ax_to_sreg[$required];
            }
            $params['openid.sreg.required'] = implode( ',', $params['openid.sreg.required'] );
        }

        if ( $this->optional )
        {
            $params['openid.sreg.optional'] = array();
            foreach ( $this->optional as $optional )
            {
                if ( ! isset( self::$ax_to_sreg[$optional] ) ) continue;
                $params['openid.sreg.optional'][] = self::$ax_to_sreg[$optional];
            }
            $params['openid.sreg.optional'] = implode( ',', $params['openid.sreg.optional'] );
        }
        return $params;
    }

    protected function axParams()
    {
        $params = array();
        if ( $this->required || $this->optional )
        {
            $params['openid.ns.ax'] = 'http://openid.net/srv/ax/1.0';
            $params['openid.ax.mode'] = 'fetch_request';
            $this->aliases = array();
            $counts = array();
            $required = array();
            $optional = array();
            foreach ( array( 'required', 'optional' ) as $type )
            {
                foreach ( $this->$type as $alias => $field )
                {
                    if ( is_int( $alias ) ) $alias = strtr( $field, '/', '_' );
                    $this->aliases[$alias] = 'http://axschema.org/' . $field;
                    if ( empty( $counts[$alias] ) ) $counts[$alias] = 0;
                    $counts[$alias] += 1;
                    ${$type}[] = $alias;
                }
            }
            foreach ( $this->aliases as $alias => $ns )
            {
                $params['openid.ax.type.' . $alias] = $ns;
            }
            foreach ( $counts as $alias => $count )
            {
                if ( $count == 1 ) continue;
                $params['openid.ax.count.' . $alias] = $count;
            }

            # Don't send empty ax.requied and ax.if_available.
            # Google and possibly other providers refuse to support ax when one of these is empty.
            if ( $required )
            {
                $params['openid.ax.required'] = implode( ',', $required );
            }
            if ( $optional )
            {
                $params['openid.ax.if_available'] = implode( ',', $optional );
            }
        }
        return $params;
    }

    protected function authUrl_v1()
    {
        $returnUrl = $this->returnUrl;
        # If we have an openid.delegate that is different from our claimed id,
        # we need to somehow preserve the claimed id between requests.
        # The simplest way is to just send it along with the return_to url.
        if ( $this->identity != $this->claimed_id )
        {
            $returnUrl .= ( strpos( $returnUrl, '?' ) ? '&' : '?' ) . 'openid.claimed_id=' . $this->claimed_id;
        }

        $params = array( 'openid.return_to' => $returnUrl, 'openid.mode' => 'checkid_setup', 'openid.identity' => $this->identity, 'openid.trust_root' => $this->trustRoot, ) + $this->sregParams();

        return $this->build_url( parse_url( $this->server ), array( 'query' => http_build_query( $params, '', '&' ) ) );
    }

    protected function authUrl_v2( $identifier_select )
    {
        $params = array( 'openid.ns' => 'http://specs.openid.net/auth/2.0', 'openid.mode' => 'checkid_setup', 'openid.return_to' => $this->returnUrl, 'openid.realm' => $this->trustRoot, );
        if ( $this->ax )
        {
            $params += $this->axParams();
        }
        if ( $this->sreg )
        {
            $params += $this->sregParams();
        }
        if ( ! $this->ax && ! $this->sreg )
        {
            # If OP doesn't advertise either SREG, nor AX, let's send them both
            # in worst case we don't get anything in return.
            $params += $this->axParams() + $this->sregParams();
        }

        if ( $identifier_select )
        {
            $params['openid.identity'] = $params['openid.claimed_id'] = 'http://specs.openid.net/auth/2.0/identifier_select';
        }
        else
        {
            $params['openid.identity'] = $this->identity;
            $params['openid.claimed_id'] = $this->claimed_id;
        }

        return $this->build_url( parse_url( $this->server ), array( 'query' => http_build_query( $params, '', '&' ) ) );
    }

    /**
     * Returns authentication url. Usually, you want to redirect your user to it.
     * @return String The authentication url.
     * @param String $select_identifier Whether to request OP to select identity for an user in OpenID 2. Does not affect OpenID 1.
     * @throws ErrorException
     */
    function authUrl( $identifier_select = null )
    {
        if ( ! $this->server ) $this->discover( $this->identity );

        if ( $this->version == 2 )
        {
            if ( $identifier_select === null )
            {
                return $this->authUrl_v2( $this->identifier_select );
            }
            return $this->authUrl_v2( $identifier_select );
        }
        return $this->authUrl_v1();
    }

    /**
     * Performs OpenID verification with the OP.
     * @return Bool Whether the verification was successful.
     * @throws ErrorException
     */
    function validate()
    {
        $this->claimed_id = isset( $this->data['openid_claimed_id'] ) ? $this->data['openid_claimed_id'] : $this->data['openid_identity'];
        $params = array( 'openid.assoc_handle' => $this->data['openid_assoc_handle'], 'openid.signed' => $this->data['openid_signed'], 'openid.sig' => $this->data['openid_sig'], );

        if ( isset( $this->data['openid_ns'] ) )
        {
            # We're dealing with an OpenID 2.0 server, so let's set an ns
            # Even though we should know location of the endpoint,
            # we still need to verify it by discovery, so $server is not set here
            $params['openid.ns'] = 'http://specs.openid.net/auth/2.0';
        } elseif ( isset( $this->data['openid_claimed_id'] ) && $this->data['openid_claimed_id'] != $this->data['openid_identity'] )
        {
            # If it's an OpenID 1 provider, and we've got claimed_id,
            # we have to append it to the returnUrl, like authUrl_v1 does.
            $this->returnUrl .= ( strpos( $this->returnUrl, '?' ) ? '&' : '?' ) . 'openid.claimed_id=' . $this->claimed_id;
        }

        if ( $this->data['openid_return_to'] != $this->returnUrl )
        {
            # The return_to url must match the url of current request.
            # I'm assuing that noone will set the returnUrl to something that doesn't make sense.
            return false;
        }

        $server = $this->discover( $this->claimed_id );

        foreach ( explode( ',', $this->data['openid_signed'] ) as $item )
        {
            # Checking whether magic_quotes_gpc is turned on, because
            # the function may fail if it is. For example, when fetching
            # AX namePerson, it might containg an apostrophe, which will be escaped.
            # In such case, validation would fail, since we'd send different data than OP
            # wants to verify. stripslashes() should solve that problem, but we can't
            # use it when magic_quotes is off.
            $value = $this->data['openid_' . str_replace( '.', '_', $item )];
            $params['openid.' . $item] = get_magic_quotes_gpc() ? stripslashes( $value ) : $value;

        }

        $params['openid.mode'] = 'check_authentication';

        $response = $this->request( $server, 'POST', $params );

        return preg_match( '/is_valid\s*:\s*true/i', $response );
    }

    protected function getAxAttributes()
    {
        $alias = null;
        if ( isset( $this->data['openid_ns_ax'] ) && $this->data['openid_ns_ax'] != 'http://openid.net/srv/ax/1.0' )
        { # It's the most likely case, so we'll check it before
            $alias = 'ax';
        }
        else
        {
            # 'ax' prefix is either undefined, or points to another extension,
            # so we search for another prefix
            foreach ( $this->data as $key => $val )
            {
                if ( substr( $key, 0, strlen( 'openid_ns_' ) ) == 'openid_ns_' && $val == 'http://openid.net/srv/ax/1.0' )
                {
                    $alias = substr( $key, strlen( 'openid_ns_' ) );
                    break;
                }
            }
        }
        if ( ! $alias )
        {
            # An alias for AX schema has not been found,
            # so there is no AX data in the OP's response
            return array();
        }

        $attributes = array();
        foreach ( $this->data as $key => $value )
        {
            $keyMatch = 'openid_' . $alias . '_value_';
            if ( substr( $key, 0, strlen( $keyMatch ) ) != $keyMatch )
            {
                continue;
            }
            $key = substr( $key, strlen( $keyMatch ) );
            if ( ! isset( $this->data['openid_' . $alias . '_type_' . $key] ) )
            {
                # OP is breaking the spec by returning a field without
                # associated ns. This shouldn't happen, but it's better
                # to check, than cause an E_NOTICE.
                continue;
            }
            $key = substr( $this->data['openid_' . $alias . '_type_' . $key], strlen( 'http://axschema.org/' ) );
            $attributes[$key] = $value;
        }
        return $attributes;
    }

    protected function getSregAttributes()
    {
        $attributes = array();
        $sreg_to_ax = array_flip( self::$ax_to_sreg );
        foreach ( $this->data as $key => $value )
        {
            $keyMatch = 'openid_sreg_';
            if ( substr( $key, 0, strlen( $keyMatch ) ) != $keyMatch )
            {
                continue;
            }
            $key = substr( $key, strlen( $keyMatch ) );
            if ( ! isset( $sreg_to_ax[$key] ) )
            {
                # The field name isn't part of the SREG spec, so we ignore it.
                continue;
            }
            $attributes[$sreg_to_ax[$key]] = $value;
        }
        return $attributes;
    }

    /**
     * Gets AX/SREG attributes provided by OP. should be used only after successful validaton.
     * Note that it does not guarantee that any of the required/optional parameters will be present,
     * or that there will be no other attributes besides those specified.
     * In other words. OP may provide whatever information it wants to.
     *     * SREG names will be mapped to AX names.
     *     * @return Array Array of attributes with keys being the AX schema names, e.g. 'contact/email'
     * @see http://www.axschema.org/types/
     */
    function getAttributes()
    {
        if ( isset( $this->data['openid_ns'] ) && $this->data['openid_ns'] == 'http://specs.openid.net/auth/2.0' )
        { # OpenID 2.0
            # We search for both AX and SREG attributes, with AX taking precedence.
            return $this->getAxAttributes() + $this->getSregAttributes();
        }
        return $this->getSregAttributes();
    }
}

?>